Stroke adjustment means for cylinder and piston assembly



Oct. 2 9, 19 68: A. F. WEISS 3,407,710

STROKE ADJUSTMENT MEANS FOR CYLINDER AND PISTON ASSEMBLY Filed Dec. 14,1966 46 e2 48 FIG. I

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INVENTOR 5 m ADOLF F WEISS i I ;QM

ATTORNEY United States Patent 3,407,710 STROKE ADJUSTMENT MEANS FORCYLINDER AND PISTON ASSEMBLY Adolf F. Weiss, Easton, Pa., assignor toAlpha Press Company, doing business as Alpha Industrial Center, Alpha,

N.J., a corporation of New Jersey Filed Dec. 14, 1966, Ser. No. 601,791Claims. (CI. 92-13) ABSTRACT OF THE DISCLOSURE A stroke adjusting meansfor a hydraulic cylinder and piston assembly which includes a casingcoupled to the cylinder and communicating with the interior thereof toreceive the pressurized hydraulic fluid. A threaded shaft is disposedwithin the casing and is connected to the piston for movement therewith.A nut is carried by the threaded shaft and a sleeve means is engagedwith the nut to normally prevent rotation thereof but to permit the nutto move axially in the casing as the threaded shaft moves. The nutcontacts against a stop means to limit the stroke of the cylinder andpiston assembly. By rotating the sleeve means, the axial position of thenut along the threaded shaft can be varied to thereby vary the stroke ofthe assembly.

This invention relates to a stroke adjustment means for a cylinder andpiston assembly and more particularly it relates to a positivemechanical stroke stop means whose position can be selectively adjustedto vary the stroke of a hydraulic assembly and of a member operated ormoved thereby.

The present invention finds particular utility in hydraulic presseswhich are used for compacting operations. In a press of this type,either a powder or slurry material is introduced into a die cavity and apair of cooperating and relatively moving punches or tool memberscompact the material to form a particular pressed article. A common typeof hydraulic press utilizes a bottom punch or tool which is fixed inposition and an upper punch or tool which is mounted on a platen whichin turn is operated by a hydraulic cylinder and piston assembly. Thematerial to be compacted is introduced into a die cavity between thetools or punches and the upper punch is thereafter lowered throughoperation of the hydraulic cylinder and piston assembly to properlycompact the material in the die cavity and to form the finished article.The degree of movement of the upper tool or punch therefore determinesthe height of the article being pressed and the amount of density orcompaction thereof, and as a result, it is important that this degree ofmovement be very accurately controlled.

There have, in the prior art, been proposals and attempts to entirelydispense with a stroke adjusting mechanism and to merely use shims orthe like to control the height of the article being pressed. This,however, was found to be a rather crude and inaccurate system involvinglong periods of trial and error. There have also been varioussuggestions to use some type of a stroke adjusting device for thepurpose described hereinabove, but such prior art stroke adjustingdevices have not been found to be wholly satisfactory. For example, onesuggestion was to place adjustable stop means in the form of elongatedscrews or the like on the upper platen, but again this was a coarse typeof adjustment device and it failed to take into account platendeflection under load. Another example of a prior art stroke adjustingdevice utilized limit switch signals which controlled a hydraulic flowarrangement to and from the cylinder and piston assembly, but again thissystem was not accurate enough for precision compacting of articles.

By far the most common type of prior art stroke ad- 3,407,710 PatentedOct. 29, 1968 justing device, and one which has heretofore been usedwith some success, is a mechanical stop means coupled to the pistonitself. That is, in the conventional cylinder and piston assembly, thepiston rod extends between the piston and the platen to be moved. Toform a mechanical stroke stop for this arrangement, an auxiliary rodwould extend from the other face of the piston and would carry a stopnut or the like at the outer end thereof. One disadvantage which hasbeen found with this system is that the length of the auxiliary rodbetween the piston and the maximum adjusted position of the stop nutmust be at least equal to the length of the cylinder. Then, the threadedportion at the outboard end of the auxiliary rod along which the stopnut can be adjusted, must be somewhat substantial in length, and as aresult, to use a stop arrangement of this type, the overall assembly wasapproximately triple the normal cylinder length. Naturally, this meantthat if the assembly was mounted on the top of a hydraulic press, extraclearance space had to be provided and the adjustment had to beaccomplished quite high above the machine. However, another and perhapseven more serious disadvantage resided in the fact that the provision ofthe auxiliary rod changed the effective surface area of the piston. Thatis, the normal piston is circular in crosssection and hence has acircular face of a preselected area upon which the pressure can act tomove the piston rod and the attached platen. However, when the auxiliaryrod is attached to this circular piston face, the effective surface areathereof is converted from a circular shape to an annular shape.Therefore, to get the same force output acting upon the platen, it isnecessary to increase the bore of the cylinder until the surface area ofthe annulus is the same as the surface area of the circular piston wouldhave been before the auxiliary rod was connected thereto. The larger thebore of a cylinder becomes, the more expensive the cylinder and pistonassembly is, and as a result, it is desirable to utilize the minimumcylinder bore consistent with the forces desired to be produced.

As a result of the foregoing consideration, it will be appreciated thatprior art attempts to provide an adjustable stop means for limiting thestroke on a hydraulic press have not been altogether satisfactory. Oneof the principal objects of the present invention is to overcome thedifficulties and deficiencies associated with such prior art forms ofstroke adjusting devices and to provide in their stead, a new andimproved stroke adjusting mechanism. However, it should be appreciatedthat the principles of the present invention are in no way limited tostroke adjusting devices which are useful on hydraulic presses, butinstead, are applicable to any situation wherein the stroke of ahydraulic unit is to be selectively adjusted.

Another object of the present invention is to provide a strokeadjustment mechanism which operates in a simple and efiicient manner andwhich can be easily controlled, yet which is highly accurate andreliable.

Another object of the present invention is to provide a stroke adjustingdevice which can readily be adapted to already existing cylinder andpiston assemblies without the need for increasing the bore size of thecylinder and without decreasing the effective forces exerted thereby.

Another object of the present invention is to provide a stroke adjustingdevice which is particularly adapted for use on a hydraulic press forcompacting materials and which can very accurately and reliably controlthe degree of compaction of such materials, while assuring that thetools or punches utilized in such a press cannot inadvertently crushagainst one another, even in the total absence of a supply of material.

Other objects, advantages and salient features of the present inventionwill become apparent from the following detailed description, which,taken in conjunction with the annexed drawings, discloses a preferredembodiment thereof.

Referring to the drawings:

FIGURE 1 is a longitudinal sectional view of the stroke adjusting meansof the present invention in combination with a conventional hydrauliccylinder and piston assembly; and

FIGURE 2 is a transverse sectional view taken substantially along theline 22 of FIGURE 1.

In accordance with the principles of the present invention, and as shownin FIGURE 1, there is provided a hydraulic unit in the form of aconventional hydraulic cylinder and piston assembly generally designatedand a control means or stroke adjusting means generally designated 12for selectively adjusting the stroke of the assembly 10.

The conventional cylinder and piston assembly 10 includes an elongatedcylinder body 14 having a pair of opposed end members 16 and 18. Aseries of spaced tie rods 20 extend through the end members 16 and 18and when the nuts 22 at the outer ends of these tie rods are tight ened,they tend to draw the end members 16 and 18 toward one another. Suitablesealing means, such as O-rings 24 or the like, can be utilized toprevent any leakage from occurring between the cylinder body 14 and theend members.

The end member 16 is provided with a hydraulic port 26 and the endmember 18 is provided with a similar hydraulic port 28. These hydraulicports are adapted to be connected through suitable piping or the likewhich forms no part of the present invention, to a source of prossurizedfluid. This pressurized fluid, which can be any suitable form ofhydraulic fluid, is introduced through the ports to the interior of thecylinder body 14. Flow through the ports 26 and 28 is reversible, asindicated by the arrows juxtaposed thereto.

A piston 30 is disposed Within the cylinder and includes a pair ofopposed substantially parallel faces 32 and 34. The maximum positionwhich the piston can be moved is from a position whereat the face 32contacts the end member 16 to an opposite position whereat the face 34contacts the end member 18. The total amount of this movement isregarded as the stroke of the assembly 10.

A piston rod 36 is afiixed to the face 34 of the piston and extends orprojects beyond the end member 18 through a central opening formedtherein. A suitable sealing means, such as a bushing 38 or the like, ismounted in this opening in the end member 18 to prevent the hydraulicfluid in the cylinder from leaking therepast. The piston rod 36 cancarry at its outboard end, an enlarged plate or flange 40 which isprovided with suitable bolt holes. Thus, any member to be moved can besuitably attached to this plate. As designated in phantom lines inFIGURE 1, a suitable member M in the form of a platen or the like can beattached thereto. It will thus be appreciated that any increment ofmovement of the piston 30 within the cylinder will cause a correspondingincrement of movement of the member M. Hence, as the stroke or degree ofmovement of the piston 30 is selectively varied, the degree of movementof the member M is likewise varied. When the movement of the piston 30is stopped, the movement of the member M is likewise stopped.

Referring now to the stroke adjusting means 12, it will be seen that thesame includes a casing 42 coupled with the cylinder and piston assembly10. Specifically, the easing can be attached between the end member 16and still another end member 44, and suitable tie rod means 46 can beutilized to connect the two together. When the nuts 48 at the end ofthese tie rods 46 are tightened, the end member 44 is drawn toward theend member 16 and the casing 42 is firmly maintained in position. Anenlarged bore 50 and counterbore 52 extend through the end member 16 sothat the interior of the cylinder 14 communicates with the interior ofthe casing 42. Thus, the hydraulic cylinder supply through the port 26not only flows into the cylinder 14 but also flows into and fills theinterior of the casing 42. Suitable sealing means, such as O-rings 54 orthe like, are utilized to prevent such fluid from leaking between thecasing 42 and the end members 16 and 44.

A threaded shaft means generally designated 56 is disposed within thecasing 42 and is coupled to the face 32 of the piston 30. In the formshown in FIGURE 1, the means 56 includes a small unthreaded stub shaft58 affixed to the face 32 of the piston and having a threaded recess 60at the outer end thereof. The threaded shaft itself includes an axiallyelongated shaft means 62 carrying screw threads 64 on the exteriorthereof, and a reduced diameter portion 66 at one end thereof whichthreads into the recess 60. The opposite end of the shaft 62 can carry aflat end plate 68. The diameter of the stub shaft 58 and the threadedshaft 62 is less than the diameter of the bore 50 so that the same willnot interrupt fluid cross flow between the casing 42 and the cylinder14. However, by providing the expedient of a separate threaded shaft 62and stub shaft 58, it is possible to use various different types ofthreaded shafts 62 having different screw threads 64 thereon. In thepreferred embodiment of the invention, the screw threads 64 are of thebuttress type arranged to transmit power unidirectionally toward thepiston 30.

A nut 70 is mounted upon the threaded shaft 62 and is movable axiallytherealong when such nut and shaft are rotated relatively to oneanother. That is, as can be seen, the nut 70 is provided with a buttressthreaded internal bore which cooperates and meshes in interengagementwith the screw threads 64 on the shaft 62. The nut 70 includes at leastone opening means therein, and in the illustrated form of invention, ascan best be seen in FIGURE 2, is provided with two slots or channels 72along the periphery thereof.

The control means 12 further includes a nut engaging means disposedWithin the casing 42 and generally designated 74. This nut engagingmeans includes an axially elongated sleeve 76 disposed in surroundingrelationship to the threaded shaft 62. The sleeve 76 carries a pair ofinternal ribs 78 which extend along the length thereof, and as will beseen in FIGURE 2, such ribs 78 fit within the channels 72 in the nut 70.The fit between the channels 72 and the ribs 78 is a relatively looseone which permits the nut to be reciprocated or moved axially relativeto the sleeve, but which prevents rotation of the nut 70 relative to thesleeve 76.

The sleeve 76 also includes an end face 80 disposed adjacent the endface 68 on the threaded shaft 62 but in spaced relation thereto. The nutengaging means 74 further includes a projecting portion in the form of ashaft 82 which projects through the end member 44 and beyond. A suitableseal means in the form of a housing 84 having various sealing ringssurrounds the shaft 82 as the same extends through the end member 44. Inthis manner, the hydraulic fluid is prevented from leaking through theend member 44. To assure a complete circulation of hydraulic fluidwithin the casing 42, both interiorly and exteriorly of the sleeve 76,an air vent 86 is provided in the face 80 of the sleeve, a similar airvent 88 is provided in the end member 44, and an air vent plug 90 ismounted therewithin. Thus, any air trapped within the control means 12will be expelled.

To continue with the description of the adjusting means portion of thenut engaging means 74, the projecting shaft 82 has a reduced diameterportion upon which a suitable sprocket 92 is mounted. This sprocket isheld in position by means of a locking nut 94. Although not shown, thissprocket can be engaged with a conventional chain drive which can beoperated by means of a hand wheel or the like. It will, of course, beappreciated that rotation of the sprocket 92 by the chain drive 'will inturn effect a rotation of the sleeve 76. Finally, it will be seen that acollar 96 is mounted on the lower end of the sleeve 76 for the purposeof preventing the sleeve from tilting or otherwise canting within thecasing.

With the aforementioned description in mind, the operation of thepresent invention can now be described. It will, of course, beappreciated that the nut 70 serves as the adjustable stop element. Theposition of this nut axially along the length of the threaded shaft 62is adjusted through operation of a nut engaging means. Specifically, thesprocket 92 is suitable rotated to effect a concurrent rotation of thesleeve 76. As the sleeve rotates about the threaded shaft 62, the ribs78 in engagement with the nut 70 cause the nut to be likewise rotated.Such relative rotation between the nut and the threaded shaft causes thenut to move axially along the shaft, either upwardly or downwardly, asdesired. When the nut finally reaches the selected axial location alongthe threaded shaft 62, rotation of the sprocket 92 is terminated androtation of the sleeve 76 is likewise terminated. Then, hydraulic fluidcan be introduced through the port 26 to move a piston 30 within thecylinder 14. It will be understood and appreciated that the pressure ofsuch hydraulic fluid acts upon the face 32 of the piston which isannular in formation due to the presence of the stub shaft 58, but it'likewise acts upon the end 68 of the threaded shaft. Hence, the totalfluid pressure applied is equal to the cross-sectional area of thepiston 30, and as such pressure is applied, the piston starts to movedownwardly in the embodiment illustrated in FIGURE 1. As such pistonmoves downwardly, the threaded shaft 62 moves axially and the nut 70carried thereby likewise moves axially. Since the only engagementbetween the nut 70 and the nut engaging means 74 is the rib and channelengagement best illustrated in FIGURE 2, axial movement of the nut isnot prevented. Thus, such nut will move downward until it contacts astop means against which it abuts. In the illustrated form of invention,the stop means is the shoulder 98 of the counterbore 52. When the nutabuts against that surface, further axial movement is prevented, andaccordingly, movement of the cylinder and piston assembly is stopped.

It will, of course, be appreciated that other suitable forms of stopmeans can be utilized. The only purpose for providing the counter-bore52 is to reduce the total excess height needed for the stop adjustingmeans 12. If desired, such counterbore can be entirely eliminated sothat the nut 70 would abut against the level top surface of the endmember 16. :In fact, if desired, an inwardly projecting flange could beprovided from the casing 42 itself, with such flange extending beneaththe lower end of the sleeve 76. In such event, this flange would serveas the stop means against which the nut 70 abuts. It will also be seenand appreciated that in the preferred form of embodiment of theinvention, the piston rod 36, the threaded shaft means 56 and theprojecting shaft 82 for the adjusting means are all coaxially aligned.

After reading the foregoing detailed description, it will be apparentthat the objects set forth at the outset of the specification have beensuccessfully achieved by the present invention. Accordingly, what isclaimed is:

1. In the combination of (1) a hydraulic unit including a cylindermeans, a piston movably mounted within said cylinder means and a pistonrod coupled with one face of said piston and adapted to be connectedwith a member to be moved, the movement of said member being controlledby the stroke of said hydraulic unit, and (2) a control means foradjusting the stroke of said hydraulic unit; the improvement in saidcontrol means comprising:

a casing coupled with said cylinder means and communicating with theinterior thereof whereby hydraulic fluid introduced into said cylindermeans will likewise be introduced into said casing;

a threaded shaft disposed within said fluid in said casing and coupledwith said piston rod;

said face coupled with said piston rod;

a nut mounted upon said threaded shaft and being movable axiallytherealong through relative rotation between said nut and said threadedshaft;

nut engaging means disposed within said fluid in said casing and engagedwith said nut to normally prevent rotation thereof while permittingaxial movement thereof as said threaded shaft is axially moved due tomovement of said piston;

said nut engaging means including adjusting means for rotating said nutengaging means and for thereby rotating said nut to adjust the positionthereof axially along said threaded shaft; and,

stop means interposed in the path of axial movement of said nut whereby,when said nut abuts thereagainst, further axial movement of saidthreaded shaft is prevented and hence the movement of said piston andpiston rod is terminated;

said abutting of said nut against said stop means thereby limiting thestroke of said hydraulic unit and the axial position of said nut alongsaid threaded shaft serving to adjust said stroke.

2. The improvement defined in claim 1 wherein said nut engaging meansincludes a sleeve means rotatably mounted within said casing.

3. The improvement defined in claim 2 wherein said sleeve meanssurrounds said threaded shaft and said nut and includes at least oneportion engageable with said nut.

4. The improvement defined in claim 3 wherein said nut includes at leastopening means therein and wherein said portion is disposed within saidopening means.

5. The improvement defined in claim 4 wherein said opening means is agroove in the periphery of said nut and wherein said portion is a ribextending along the interior of said sleeve means.

6. The improvement defined in claim 1 wherein said nut engaging meansincludes a projecting portion extending exteriorly of said casing toform at least a part of said adjusting means.

7. The improvement defined in claim 6 further including a collar meansmounted upon said projecting portion whereby rotation of said collarmeans rotates said nut engaging means.

8. The improvement defined in claim 6 wherein said piston rod, saidthreaded shaft and said projecting portion are coaxially aligned.

9. The improvement defined in claim 1 wherein the end of said threadedshaft remote from said piston is free from contact with said nutengaging means whereby said hydraulic fluid can exert a pressure forcethereagainst so that the eifective pressure area of said piston is notreduce-d through coupling of said threaded shaft thereto.

10. The improvement defined in claim 1 wherein said cylinder meansincludes end members, wherein said casing means abuts against one ofsaid end members and wherein at least a portion of said one end memberforms said stop means. 1

References Cited UNITED STATES PATENTS 1,325,006 12/ 1919 Deansley 92-131,571,044 1/1926 De Costa 92-13 X 2,346,868 4/1944 Perry 92-13 X2,640,325 6/ 1953 Haller 9213 2,674,098 4/ 1954 Taylor 9213 X 2,761,4249/1956 Hopkins 92-13 X 3,136,227 6/1964 Williams 92-63 FOREIGN PATENTS739,140 10/ 1955 Great Britain.

MARTIN P. SCHWADRON, Primary Examiner. I. C. COHEN, Assistant Examiner.

